1. Field of the Invention
The present invention relates to an electric power steering device.
2. Description of the Related Art
Japanese Patent Application Laid-Open (JP-A) No. 2009-51354 describes, as an electric power steering device, a device constructed by providing an input shaft to which a steering wheel is connected, an output shaft connected to a wheel side, a torsion bar provided between the input shaft and the output shaft, a torque sensor that detects steering torque input from the steering wheel, an electric motor driven in accordance with the torque detected by the torque sensor, and a worm wheel provided on the output shaft to transmit rotation of the electric motor to the output shaft in a housing.
In an electric power steering device described in JP-A No. 2009-51354, a supporting structure for the housing of the output shaft for which the worm wheel is provided is as follows.
A boss of the worm wheel is fitted into an outer circumference of the output shaft and bearings are fitted into two positions on both sides sandwiching the boss of the worm wheel on the output shaft to support these two bearings on the housing.
Therefore, the boss of the worm wheel and the two bearings are aligned in a row in an axial direction of the output shaft and there is a large space to support the output shaft inside the housing.
As a positioning structure of the bearing on the output shaft, a ring protrusion provided on the outer circumference of the output shaft or a special positioning structure such as a nut screwed into the outer circumference of the output shaft is used. This also increases the required support space of the output shaft inside the housing.